Results from the OptiControl Project

We present selected results from the project "Use of Weather and Occupancy Forecasts for Optimal Building Climate Control" (OptiControl), a Swiss project that involved researchers and engineers from ETH Zurich, Siemens Building Technologies, EMPA Materials Science & Technology, the Swiss Federal Office of Meteorology and Climatology, and the Gruner AG engineering and consulting company. The project focused on the so-called "Integrated Room Automation" (IRA) for office buildings. IRA deals with the automated control of blinds, electric lighting, heating, cooling and ventilation of a building zone or room and therefore covers many aspects of modern building control. Five different technical system variants involving different combinations of heating, cooling and ventilation subsystems were considered.
Based on extensive simulation studies the average theoretical annual energy savings potential of predictive control was found to be 16%â41%, depending on the building zone characteristics and the choice of technical building system. This compares to average savings of 13%â28% thanks to the use of CO2-controlled ventilation instead of non-air quality controlled ventilation; of 6%â16% due to a widening of the thermal comfort range by ~1.5 degC; of 0%â18% thanks to the the allowance for night/weekend room temperature set-backs; and of 1%â15% achievable by improved non-predictive control.
Generally, all savings potentials were found to vary widely with location, building case, and technical system. The savings potentials of predictive control were mainly due to improved management of building thermal mass thanks to optimized control of blinds/solar heat gains and of free cooling.
A further major project result were stochastic Model Predictive Control (MPC) algorithms that allow for integration of weather forecasts and for the management of peak electricity demand. Detailed analyses for a range of representative building cases demonstrated substantial benefits of the newly developped MPC algorithms as compared to conventional, non-predictive rule-based control. Advantages were found in terms of energy usage, robustness, tunability, flexibility (e.g., optional limitation of peak power demand, either directly, or in response to time-varying electricity prices), and comfort.
Further results were: (i) Improved rule-based, non-predictive, and novel rule-based pre-dictive IRA control algorithms, plus associated tuning rules; (ii) new algorithms for delivering hourly temperature and radiation forecasts at a buildingâs location at the high quality required by predictive controllers; (iii) a general and flexible, MATLAB-based modelling and simulation environment for the study of building control in individual building zones. The environment includes databases for buildings, building technical systems, weather, weather forecasts, and occupancy data. Next to being a unique research and development tool the software provided also the basis for a web-based tool that supports the online assessment of predictive control strategies also for non-expert users (www.bactool.ethz.ch).
In summary, the OptiControl project has successfully answered many important questions related to the potential and feasibility of predictive building control, and it has paved the way towards the development of a new generation of controllers offering improved performance, robustness and flexibility. A follow-up project that starts in April 2011 aims at the practical demonstration of the proposed control solutions in a typical Swiss office building and the development of industry-compatible prototypes.